8.2

• Nervous system


  Can be divided into central nervous system and peripheral nervous system
• Central nervous system (CNS)


  Consists of the brain and spinal cord
• Peripheral nervous system (PNS)


  Consists of all the nerves and ganglia outside the brain and spinal cord
• Spinal cord


  • Extends from the foramen magnum to the 2nd lumbar vertebra
  • Protected by vertebral column
  • Spinal nerves allow movement
  • If damaged paralysis can occur
• Gray matter


  Center of spinal cord, looks like letter H or a butterfly
• White matter


  Outer layer of spinal cord, contains myelinated fibers
• Columns in white matter of spinal cord

  • Dorsal
  • Ventral
  • Lateral
• Ascending tracts


  Axons that conduct action potentials toward the brain
• Descending tracts


  Axons that conduct action potentials away from the brain
• Gray matter in spinal cord

  • Has a letter H shape with horns
  • Posterior horns contain axons which synapse with interneurons
  • Anterior horns contain somatic neurons
  • Lateral horns contain autonomic neurons
  • Central canal is fluid filled space in center of cord
• Reflex


  Involuntary reaction in response to a stimulus applied to the periphery and transmitted to the CNS
• Reflex arc


  • Neuronal pathway by which a reflex occurs
  • Has five basic components: sensory receptor, sensory neuron, interneurons, motor neuron, effector organ
• Stretch reflex


  Muscles contract in response to a stretching force applied to them
• Withdrawal reflex


  To remove a limb or another body part from a painful stimulus
• Spinal nerves

  • Arise along spinal cord from union of dorsal roots and ventral roots
  • Contain axons of sensory and somatic motor neurons
  • Located between vertebra
  • Categorized by region of vertebral column from which it emerges (C for cervical)
  • 31 pairs organized in 3 plexuses
• Cervical plexus


  • Spinal nerves C1-4
  • Innervates muscles attached to hyoid bone and skin of neck and back of head
  • Contains the phrenic nerve which innervates diaphragm
• Brachial plexus


  • Originates from spinal nerves C5-T1
  • Supply nerves to the upper limbs, shoulders, hand
• Lumbosacral plexus


  • Originates from spinal nerves L1 to S4
  • Supplies nerves lower limbs
• Dermatome


  Area of skin supplied with sensory innervation by a pair of spinal nerves
• Major regions of the brain

  • Brainstem
  • Cerebellum
  • Diencephalon
  • Cerebrum
• Brainstem


  • Components: Medulla oblongata, Pons, Midbrain
• Medulla oblongata


  Regulates heart rate, blood vessel diameter, breathing, swallowing, vomiting, hiccupping, coughing, sneezing, balance
• Pons


  Involved in breathing, chewing, salivation, swallowing, relay station between cerebrum and cerebellum
• Midbrain


  Coordinates eye movement, pupil diameter, turning head toward noise
• Reticular formation


  Regulates cyclical motor function, respiration, walking, chewing, arousing and maintaining consciousness, regulates sleep-wake cycle
• Cerebellum


  • Attached to the brainstem by the cerebellar peduncles
  • Cortex is composed of gyri, sulci, gray matter
  • Controls balance, muscle tone, coordination of fine motor function
• Diencephalon


  • Components: Thalamus, Hypothalamus, Epithalamus
• Thalamus


  Regulates sensory input traveling from the spinal cord and brainstem to the cerebral cortex, influences moods and detects pain
• Epithalamus


  Involved in emotional and visceral response to odors, contains the pineal gland which plays a role in controlling some long-term cycles that are influenced by the light-dark cycle
• Hypothalamus


  Controls homeostasis, body temp, thirst, hunger, fear, rage, sexual emotions, controls pituitary gland
• Cerebrum


  • Largest portion of brain
  • Divided into right and left hemispheres separated by longitudinal fissure
  • Lobes: frontal, parietal, occipital, temporal, insula
• Cerebral cortex


  Surface of cerebrum, composed of gray matter, controls thinking, communicating, remembering, understanding, and initiates voluntary movements
• Cerebral surface features

  • Longitudinal fissure divides cerebrum into left and right hemispheres
  • Gyri are folds on cerebral cortex that increase surface area
  • Sulci are shallow indentations
  • Fissures are deep indentations
• Left hemisphere


  Controls right side of body, responsible for math, analytic, and speech
• Right hemisphere


  Controls left side of body, responsible for music, art, abstract ideas
• Corpus callosum


  Connection between the two cerebral hemispheres
• Frontal lobe


  • Controls voluntary motor functions, aggression, moods, smell
• Parietal lobe


  • Evaluates sensory input such as touch, pain, pressure, temperature, taste
• Occipital lobe


  • Vision
• Temporal lobe


  • Hearing, smell, memory